So just to get this right, I will have it fused no more than 12" from both batteries positive connections to the relay and a circuit breaker no more than 12" from battery #2 on the positive connection to my amps? Thanks for all the help on this.

So just to get this right, I will have it fused no more than 12" from both batteries positive connections to the relay and a circuit breaker no more than 12" from battery #2 on the positive connection to my amps? Thanks for all the help on this.

Think about what would happen if the positive cable is somehow cut and shorts to ground. With only one side protected, the other battery will send everything it has to ground. A cable will dump a lot of current when this happens and if it exceeds the cables capacity, the resistance causes the cable to get hot and if there's no way to cut the current flow, the insulation will burn and take the boat with it. The only time this will stop is when the wire is thin enough to fuse, which breaks the connection.

Personally, I like breakers. They can be reset, they can be opened when work is done to the system and if it opens, it doesn't cost $8 to buy another one.

I have a question. What happens if you occasionally charge a starting and deep cell battery in parrellel? I have a starting and deep cell setup right now and have been keeping the perko switch on the deep cell. Only switch to the cranking if the deep cell is dead. I know some people have said not to do it but I want to understand why and the effects if anyone knows.

I have a question. What happens if you occasionally charge a starting and deep cell battery in parrellel? I have a starting and deep cell setup right now and have been keeping the perko switch on the deep cell. Only switch to the cranking if the deep cell is dead. I know some people have said not to do it but I want to understand why and the effects if anyone knows.

You mean charging it using the alternator? It beats the crap out of the alternator and won't charge them as well as they need because unless the alternator can support a lot of current and they're isolated, one will always draw more than the other.

Cranking batteries exist for a reason- they deliver high current quickly and recover quickly. A deep cycle is usually made to deliver current over a longer time period and recover after being discharged deeper than a cranking battery. If you really want more info about your specific batteries, contact the manufacturer and tell them what the item number is.

Jim if I run an isolator or relay instead of the perko switch will I be able to run the cranking and deep cell? Or should I try to just get another deep cell or go all cranking? The deep cell I have is huge and gives me 710 CCA with 150 mins at 25 amps that is why the cranking is more of a back up.

Jim if I run an isolator or relay instead of the perko switch will I be able to run the cranking and deep cell? Or should I try to just get another deep cell or go all cranking? The deep cell I have is huge and gives me 710 CCA with 150 mins at 25 amps that is why the cranking is more of a back up.

If you get to the point where the big deep cycle is low (never kill it completely), just switch over to the cranking battery and run it back home. When you do this, use a charger on the deep cycle.

I have a 1994 Prostar 205. I installed a sony marine receiver (just a simple head, no amp, etc) and powered it from the harness that was labeled behind the dash. It powers when the key is in acc or ignition is on. I hooked up the memory thru the acc1 switch so I could control it - leaving it on during outings so I can set presets at the beginning of the day and they stay, but I can turn it off and know that I have zero drain.
I would like to add a dual battery with the relay setup because it seems like great piece of mind. In reading the instructions, I see that they say to move accessories to the second battery. Well, I went to the battery and expected to see additional wires for the accessories. But there is just one big cable on each battery terminal. There is an accessory wire dangling with a fuse on it that is not attached to the battery. it runs up the drivers side and under the dash. It is cut and capped there.
Do I need a dual battery setup for such a small radio? Should I wire just the radio to the second battery using the unused wires rather than the dash/harness? And leave all other things as they are? Then the second battery will be for JUST my radio?
I was hoping I could feed all accessories somehow by using the harness. I would need to know where the harness gets its power for the accessories and hook the secondary battery up there. Then I would have the dual battery protection when I used lights too while floating at night with the motor off.

Having owned a 1994 Prostar 205, there no convenient place to put a second battery. I would get one of those portable jump battery pack and keep it under the seat for situations where a second battery would come in handy. With your stereo configuration, it would take a very long time to drain the battery, unless you have a weak battery to start off with.

Thanks for the reply. I might just do that. I am also a bit nervous about adding a relay in the compartment behind the back seat where the gas tank is. If that thing arcs while there are fumes built up in that compartment that would not be good!